Our central goal is the clinical evaluation of the role of modulated energy proton beam in conventionally fractionated radiation therapy. The two major aspects of this work are: 1) determination of the effect of tissue heterogeneities upon dose distribution patterns in vivo (this includes determination of most appropriate technique for study of density distribution within tissues, precision required to avoid unsuspected cold spots in actual treatment); and 2) evaluation of proton therapy on those clinical situations where the proton dose distribution pattern appears to offer clinically important advantages. Additionally we need to assess the RBE of the various beam sizes and modulation patterns; the RBE is expected to be less than 1.05; even so, we must have good values for the RBE in planning medical radiation therapy because of the extreme steepness of the dose response curve for normal tissues.